diff --git a/embassy-executor/src/lib.rs b/embassy-executor/src/lib.rs index 6a2e493a2a..553ed76d3d 100644 --- a/embassy-executor/src/lib.rs +++ b/embassy-executor/src/lib.rs @@ -1,4 +1,5 @@ #![cfg_attr(not(any(feature = "arch-std", feature = "arch-wasm")), no_std)] +#![cfg_attr(feature = "nightly", feature(waker_getters))] #![allow(clippy::new_without_default)] #![doc = include_str!("../README.md")] #![warn(missing_docs)] diff --git a/embassy-executor/src/raw/waker.rs b/embassy-executor/src/raw/waker.rs index 522853e346..fe64456e16 100644 --- a/embassy-executor/src/raw/waker.rs +++ b/embassy-executor/src/raw/waker.rs @@ -32,6 +32,7 @@ pub(crate) unsafe fn from_task(p: TaskRef) -> Waker { /// # Panics /// /// Panics if the waker is not created by the Embassy executor. +#[cfg(not(feature = "nightly"))] pub fn task_from_waker(waker: &Waker) -> TaskRef { // safety: OK because WakerHack has the same layout as Waker. // This is not really guaranteed because the structs are `repr(Rust)`, it is @@ -46,7 +47,31 @@ pub fn task_from_waker(waker: &Waker) -> TaskRef { unsafe { TaskRef::from_ptr(hack.data as *const TaskHeader) } } +#[cfg(not(feature = "nightly"))] struct WakerHack { data: *const (), vtable: &'static RawWakerVTable, } + +/// Get a task pointer from a waker. +/// +/// This can be used as an optimization in wait queues to store task pointers +/// (1 word) instead of full Wakers (2 words). This saves a bit of RAM and helps +/// avoid dynamic dispatch. +/// +/// You can use the returned task pointer to wake the task with [`wake_task`](super::wake_task). +/// +/// # Panics +/// +/// Panics if the waker is not created by the Embassy executor. +#[cfg(feature = "nightly")] +pub fn task_from_waker(waker: &Waker) -> TaskRef { + let raw_waker = waker.as_raw(); + + if raw_waker.vtable() != &VTABLE { + panic!("Found waker not created by the Embassy executor. `embassy_time::Timer` only works with the Embassy executor.") + } + + // safety: our wakers are always created with `TaskRef::as_ptr` + unsafe { TaskRef::from_ptr(raw_waker.data() as *const TaskHeader) } +}